Delusional Disorder: Paranoia and Related Illnesses

Along with schizophrenia and major mood disorders, paranoid or delusional disorders have traditionally been considered an important group of functional psychoses. In fact, in the ICD nomenclature, paranoid psychoses (now referred to as delusional disorders) are assigned a full three-digit code (297), just as schizophrenia (295) and major mood disorders (296) are. Despite this official recognition, however, this group of disorders remains mysterious to a vast majority of clinicians and researchers. Even though paranoid psychoses have been part of the official nomenclature (from ICD-8 to ICD-10 and from DSM-I to DSM-IV) from the 1950s to the present, the concept fell into relative disuse over this period of time. From the 1950s through the 1980s, much of this category was subsumed under schizophrenia, and now a substantial portion of this entity is being classified as psychotic mood disorder or schizoaffective disorder.

What is the evidence that delusional disorders constitute a unique group of psychiatric disorders, distinct from other psychiatric disorders with regard to clinical features, course, prognosis, response to treatment, family history, etc.? What is the evidence that different delusional disorders are more similar than dissimilar with regard to the above characteristics, warranting their categorization as a group of delusional disorders? What are the boundaries of this group of disorders? What is the current status of our knowledge about the clinical characteristics, etiology, pathophysiology, treatment, and prognosis of the various delusional disorders? What conditions can potentially be confused with various delusional disorders, and how does one make necessary clinical distinctions? What is known about the treatment of various delusional disorders?

In Delusional Disorder: Paranoia and Related Illnesses, Alistair Munro addresses all of the above issues and provides a scholarly review of this group of disorders. Culling material from multiple sources, Munro provides a comprehensive and yet eminently readable overview of paranoia and related delusional disorders. The book has 14 chapters grouped in five parts. In the introduction, the author reviews the history of the disorder and discusses why it has been somewhat elusive. The discussion of the phenomenology and nosological implications and the guide to practical assessment of delusions at the end of this chapter are outstanding.

In the second section, composed of five chapters, Munro provides a comprehensive clinical description of delusional disorder and its somatic, jealousy, erotomanic, persecutory, and grandiose subtypes. The author notes the fundamental similarity in the form of psychopathology between the different types of delusional disorders, which differ in their content. Although the author provides a lucid description of these different delusional disorders (richly supplemented by case material), he provides a scant discussion of how to delimit delusional disorder, somatic type, from psychotic depression and delusional disorder, grandiose type, from psychotic mania. In fact, throughout the book, the author extensively discusses differences between schizophrenia and delusional disorders but is rather frugal when it comes to considering the distinction between delusional disorders and psychotic mood disorders. In view of the “affective bias” that has guided our diagnostic approach since the 1980s, a substantial proportion of the conditions that the author would consider delusional disorder are currently being diagnosed as psychotic mood disorders; this discussion would have been useful. There could also have been some discussion of the sociocultural determinants of delusional content.

In the third section of the book, composed of four chapters, the author considers four conditions (paraphrenia, late paraphrenia, delusional misidentification syndrome, and folie à deux) that he thinks should be included in the category of delusional disorders. The case that he makes is forceful and persuasive. The case for considering paraphrenia and late paraphrenia as distinct delusional disorders separate from paranoid schizophrenia is debatable, however. The author comments on the relatively preserved affect and thought process along with relatively preserved social function in patients with paraphrenia; is all good-prognosis schizophrenia not really schizophrenia, then? In fact, the author also suggests the possibility that paranoid schizophrenia itself may be better classified with the delusional disorders than with the schizophrenias. Although there may be some merit to this suggestion, it is debatable at best, and the author could have provided a more complete discussion of factors that argue against this. Furthermore, he may have wanted to discuss the merits and limitations of our current categorical nosologic systems in comparison with dimensional classification.

In the fourth section, Munro provides an excellent summary of various illnesses that are not delusional disorders but are liable to be misdiagnosed as delusional disorders. In the final section, the treatment of delusional disorders is reviewed and an overall conclusion provided.

The author notes,

The author firmly and explicitly believes that delusional disorders constitute a substantial proportion of major psychiatric disorders and that the disorders are best classified together. Although he provides a comprehensive review and makes a strong case for his point of view, he agrees that the evidence is scant and that some of it is flimsy and unconvincing. All would share his hope that its validity will be tested in many more scientific ways than ever before, even though one may question his assumption that “diagnostic issues are much more alive today than they have been for a long time.”

This is an excellently researched and superbly written book. Despite its comprehensive nature, it reads easily. It is supplemented with rich clinical material; there are 28 cases described that illustrate different issues discussed. It is extremely informative and brings the reader up to speed on the rather poorly understood entity of the delusional disorders. The author dispels several myths about the delusional disorders, noting that these disorders are not rare and are eminently treatable. I enjoyed reading the book and learned much from it. I recommend it highly to both clinicians and researchers.